You can buy Instagram followers from legitimate follower sites, but remember that not all of them are reputable.
When making this purchase, protect yourself by using a secure credit card and doing as much background research on the company as possible.
Some of the major follower sites (according to wikihow) include socialmarketinghub.net, fotosprout.com and buyinstagramfollowers.biz.
You will need to pay between 5 and 10 cents for every follower you purchase. Keep in mind that most purchases will take up to 60 days in order to start showing results, so you will need to be very patient.
You can pick how many followers you are looking to buy, but the bigger numbers tend to come with larger discounts. Remember, a steady growth in followers will usually look more legitimate than a huge influx of followers that seem to appear out of nowhere or overnight.
You may also want to think about the "quality" of followers you are buying.
Some services can help you boost your follower count at a very low cost, but the profiles that follow you may be dummy Instagram accounts that do nothing on the app other than follow people. If you don't want to get found-out for buying Instagram followers, then this is something to bear in mind!